Valorisation of Vitis vinifera L. grape pomace: phenolic profile, antioxidant capacity, and inhibitory potential on glucose metabolism enzymes

The wine sector generates significant by-products, with grape pomace being one of the most plentiful. Traditionally used in distillates, fertilizers, and animal feed, grape pomace is recognized for its nutritional benefits and potential health advantages. Modern circular economy models aim to extend product lifecycles and make better use of food waste and by-products. This shift not only maximizes the value extracted from grape pomace but also promotes sustainability and environmental responsibility within the wine industry, transforming waste into valuable resources for different applications. This study aimed to compare differences in vitro methods to evaluate the phenolic profile and antioxidant capacity of grape pomace from various Vitis vinifera L. varieties, and to assess their impact on enzymes involved in glucose metabolism and glycemia regulation. Methods included Folin-Ciocalteu assay for total polyphenol content, differential pH test for total anthocyanin content, DPPH, FRAP and HPSA assay for antioxidant activity. The inhibitory effects on dipeptidyl peptidase IV (DPP-IV), pancreatic alpha-amylase, and alpha-glucosidase were also evaluated. The findings shows that spectrophotometric methods provided valuable insights into the phenolic composition of grape pomace, showing strong correlations with antioxidant activity. Grape pomace, particularly when containing seeds, proved to be a rich source of polyphenols, exhibiting substantial antioxidant properties and potential to inhibit enzymes involved in postprandial blood sugar regulation. These findings suggest that winemaking by-products such as grape pomace could be valuable sources of bioactive compounds, useful for dietary supplements and functional products, then supporting sustainable practices within wine industry.